Olympic divers gearing up to give the performance of their lives were left stunned to see that their clear blue pool of dreams had turned a gnarly shade of green.
Competitors in Rio were confronted with the funky pool during Tuesday’s synchronized diving contest – and nobody could explain what had happened.
Officials tested the water and concluded that it wasn’t dangerous – but seemed at a loss as to why the snap change had taken place.
The diving pool had been fine the previous day, and the distance swimming pool next door stayed regular blue, deepening the mystery:

Organizers couldn’t give a definitive reason why the embarrassing change had taken place, and made a laughing stock of the Maria Lenk Aquatic Centre.
The water quality at the Maria Lenk Aquatics Centre was tested and there were no risks for the athletes. We are investigating the cause.
— Rio 2016 (@Rio2016_en) August 9, 2016
Algae seemed to be the most likely culprit, especially given that the diving pool is kept warmer than its neighbour, which makes it easier for organism to grow there.
No-one will give an explanation for the green diving pool. An official statement from Rio2016 is being prepared!!!
— Dan Walker (@mrdanwalker) August 9, 2016
Another theory online suggested that a reaction with copper in the water could have sparked the change. Some who suggested peeing in the pool was to blame were swiftly shut down.
Despite the weird – and potentially distracting – reversal, the competition still went ahead.
Some optimistic competitors even embraced the green. Tonia Couch, a British diver who came 5th in the women’s 10m synchronized dive, said the bolder color made it easier to “spot” and judge her distance.
So there’s always a silver lining, even if it’s actually green.